Ethical advice

So I saw this old abandoned RP from like 2018, and I thought the characters people had made were really interesting, so I've been drawing them. I don't know who the original creators are, so I can't really credit them. Is it okay to post my drawings (non commercially ofc) on DeviantArt if I say something like, "These aren't my characters, if you created them please tell me and I'll credit you, or take it down if you want"?